It has caused a bit of noise and critics have voiced their opinion, however the local ministry for health approved it as well as the city of Düsseldorf.
Based on a statement from the Düsseldorf Ministry of Health, the concept of the organizer complies with the required hygiene procedures more than it would even need to. They are monitoring the progress of the Corona case numbers and the event organizers have left themselves the option of cancelling the event on short notice.
However it is a great sign from an event industry giant to show that it is possible and give others the confidence to follow suit.
(Now lets see how many people actually buy tickets...)